This disclosure relates generally to spinal surgery involving the lower lumbar vertebrae. More specifically, this disclosure relates to devices and methods for an intraosseous surgical approach through the sacral ala to the lumbar spine for a variety of interventions including intervertebral fixation, disc excision and/or ablation.
A significant number of adults have had an episode of back pain or suffer chronic back pain emanating from a region of the spinal column. A number of spinal disorders are caused by traumatic spinal injuries, disease processes, aging processes, and congenital abnormalities that cause pain, reduce the flexibility of the spine, decrease the load bearing capability of the spine, shorten the length of the spine, and/or distort the normal curvature of the spine. Many people suffering back pain resort to surgical intervention to alleviate their pain.
Disc degeneration can contribute to back pain. With age, the nucleus pulposus of the intervertebral discs tends to become less fluid and more viscous. Dehydration of the intervertebral disc and other degenerative effects can cause severe pain. Annular fissures also may be associated with a herniation or rupture of the annulus causing the nucleus to bulge outward or extrude out through the fissure and impinge upon the spinal column or nerves (a “ruptured” or “slipped” disc).
In addition to spinal deformities that occur over several motion segments, spondylolisthesis (forward displacement of one vertebra over another, usually in the lumbar or cervical spine) is associated with significant axial and/or radicular pain. Patients who suffer from such conditions can experience diminished ability to bear loads, loss of mobility, extreme and debilitating pain, and oftentimes suffer neurological deficit in nerve function.
Failure of conservative therapies of spinal pain such as bed rest, pain and muscle relaxant medication, physical therapy or steroid injection often leads patients to seek spinal surgical intervention. Many surgical techniques, instruments and spinal disc implants have been described that are intended to provide less invasive, percutaneous, or minimally-invasive access to a degenerated intervertebral spinal disc. Instruments are introduced through the annulus for performing a discectomy and implanting bone growth materials or biomaterials or spinal disc implants within the annulus. One or more annular incisions are made into the disc to receive spinal disc implants or bone growth material to promote fusion, or to receive a pre-formed, artificial, functional disc replacement implant.
Extensive perineural dissection and bone preparation can be necessary for some of these techniques. In addition, the disruption of annular or periannular structures can result in loss of stability or nerve injury. As a result, the spinal column can be further weakened and/or result in surgery-induced pain syndromes. One technique for spinal fixation includes the immobilization of the spine by the use of spine rods of various configurations that run generally parallel to the long axis of the spine. Typically, the posterior surface of the spine is isolated and bone screws are first fastened to the pedicles of the appropriate vertebrae or to the sacrum such that they act as anchor points for the spine rods. The bone screws are generally placed two per vertebra, one at each pedicle on either side of the spinous process.
Persistent low back pain is often attributed to degeneration of the disc connecting L5 and S1. Highly invasive techniques have been proposed for the treatment of such degeneration through surgical fixation and fusion of the lower lumbar vertebrae. For example, one technique involves a posterior approach for the removal of the painful disc and fusion of the adjacent vertebrae to relieve the low back pain. This method commonly requires extensive surgical dissection, including stripping of the paraspinal musculature and nerve retraction. Another technique is anterior lumbar fusion in which the spine is approached through the abdomen, and has associated requirements for the mobilization and/or protection of peritoneal and retroperitoneal structures. Other surgeries are designed to fuse and stabilize the intervertebral segment through a lateral approach, which commonly entails dissection through the psoas muscle and its invested lumbosacral nerves.
Another surgical approach involves access of the superior disc space through the sacral pedicles. This technique also suffers from several disadvantages. For example, approaching the L5-S1 disc space through the S1 pedicles have proven relatively difficult and impractical. The techniques are very demanding and prior surgical navigation techniques have been relatively unreliable in providing the precise navigation required to approach the L5-S1 disc space via the S1 pedicles. Due to the relative position of the S1 pedicles and the L5-S1 disc space, this approach suffers from limitations in disc space access and manipulation of surgical tools within. The approach weakens, violates and/or removes bone from the S1 pedicle(s) in a manner that could potentially compromise the sacral pedicle fixation.